The material handling industry utilizes a variety of mechanisms to lift, move, and place materials such as scrap or finished products. For relocating magnetic materials, e.g., diamagnetic metals, paramagnetic metals, and ferromagnetic metals; an electromagnet is preferable in many cases because it does not require personnel to position the chains, hooks, and other mechanical grasping mechanisms often utilized during the attachment and release of the magnetic material. Such grasping mechanisms can further mar metal surfaces and increase the possibility of product damage.
One drawback to using an electromagnetic lifting device is that the magnetic material may not readily release from the electromagnet when operated to do so. For instance, when the power source to the electromagnet is removed, the magnetic material may not immediately release and will stay attached to the electromagnet, but may eventually drop due to the force of gravity. As such, it is common to temporarily reverse the polarity of the electromagnet to repel or “push” the magnetic material from the electromagnet. The magnitude of the reverse force can be significant and as a result, some magnetic materials—e.g., ferromagnetic—may be re-attracted to a now oppositely charged electromagnet and not drop; or if released, will itself retain an undesired residual magnetism. To effect a clean drop, several factors should be considered and compensated for, including, and not limited to the operating characteristics of the electromagnet and the generator, as well as the load, temperature, and velocity of the generator.
When operating electromagnet equipment that utilizes dangerously high voltage levels, operator safety is also a major concern. A variety of safety mechanisms, e.g., circuit-breakers, have been available for safely securing machinery against ground faults, e.g., electrical shorts. One such common ground fault circuit interrupt (GFCI) is typically incorporated with electrical machinery; however the GFCI is not easily adaptable for use in electromagnetic moving equipment, which is possibly due in part to the bipolar voltage nature of the electromagnetic magnet and generator.
An innovation described herein is provided to address these and other issues.